Over a decade, Fabry-Perot (FP) based narrow band filters have been used extensively to image the solar atmosphere at various heights. The FP based filters have notable advantage of fast tunability and high light throughput compared to the Michelson interferometer and birefringent filters. However, those designs have a limitation on spectral resolution. Two or three FT etalons in seriers has better performance than just a single FP in respect of 1) high spectral resolution, 2) large spectral range, 3) large field-of-view, 4) high light throughput to have sufficient light, 5) fast change between wavelenghts 6) minimum stray light. Table 2 gives the design specifications of the FP based imaging spectrometer to meet our scientific goals
Table 2 Design specifications of the narrow band imaging system with two FP in series
